Circularly polarized antennas emit electromagnetic waves comprised of two linearly polarized electric field components that are orthogonal, equal in magnitude and are 90 degrees out of phase. These antennas are desirable due to their ability to suppress a considerable portion of non line of sight signals as well as their resistance to polarization mismatch losses.
Traditional circularly polarized microstrip antennas have limited achievable boresight gain. This is usually increased by stacking either parasitic elements or high permittivity superstrates on top of the patch, which increases antenna height as well as fabrication complexity and cost. Another method traditionally employed to increase the directivity of microstrip antennas is the use of an array of such elements printed on the substrate. While effective, this technique suffers from increased complexity as well as cost, caused by the need to feed the separate array elements. The drawback of traditional circularly polarized microstrip antennas is their inability to provide uniform coverage especially at low elevation angles.
Another limitation of the traditional circularly polarized microstrip antennas is its limited beamwidth, and their ineffectiveness in radiating co-polarized fields below the antenna horizon. One example of the need for such characteristics is in marine GPS, where pitch and roll movement of the vessel may cause the GPS receiver to lose reception from some of the transmitting satellites.
Therefore, a heretofore unaddressed need exists in the art to address the aforementioned deficiencies and inadequacies.